Since organic electroluminescent elements (which may hereinafter also be referred to as “elements” or “organic EL elements”) are capable of high-luminance light emitting with driving at a low voltage, they have been actively researched and developed. The organic electroluminescent elements have organic layers between a pair of electrodes, and utilize, for light emitting, energy of the exciton generated as a result of recombination of electrons injected from a cathode and holes injected from an anode in the organic layer. Since the organic electroluminescent elements are capable of being provided as an element having various light emitting wavelengths, have a high response speed, and are relatively thin and light-weight, it is expected that the element can be employed in a wide range of applications. Above all, it is important to develop an organic electroluminescent element having green phosphorescent light emission, low driving voltage, high luminous efficiency, and high durability in applications with full-color displays, and the like, and the outcomes of various research and development studies up to now have been reported.
PTL 1 describes an organic electroluminescent element, in which a platinum complex having a specific structure, or the like is used as a light emitting material of a light emitting layer, and also describes that a phosphorescent light emitting element having good color purity and element durability can be provided. PTL 1 describes fused aromatic carbocyclic compounds, non-complex aromatic nitrogen-containing heterocyclic compounds, and the like as an example of a host material of a light emitting layer, but discloses only Examples, in which carbazole-based compounds or beryllium complexes are used.
On the other hand, PTL 2 describes an organic electroluminescent element, in which a polycyclic fused-ring compound with 5 or more rings is used as a host material of a light emitting layer, with the use of a platinum complex having a specific structure, which is a red light emitting material, as a light emitting material of a light emitting layer. However, in PTL 2, only a material having a structure exhibiting red light emission is employed for the platinum complex, and accordingly, the performance of an organic electroluminescent element obtained in the case of using a platinum complex having a structure exhibiting green light emission is unclear.
PTL 3 describes an organic electroluminescent element, in which a polycyclic fused-ring compound with 5 or more rings is used as a host material of a light emitting layer and an iridium complex having a specific structure is used as a light emitting material of the light emitting layer, and also describes that an element having excellent luminous efficiency and durability can be provided. However, PTL 3 does not describe Examples, in which a platinum complex is used as a light emitting material.
PTL 4 describes an organic electroluminescent element, in which a polycyclic fused-ring compound with 5 or more rings is used as a host material of a light emitting layer and an iridium complex having a specific structure is used as a light emitting material of the light emitting layer, and also describes that an element excellent in terms of luminous efficiency, pixel defects, and service life can be provided. However, PTL 4 describes various platinum complexes as a light emitting material and does not describe Examples, in which a platinum complex is used.